1. Field of the Invention
The present invention relates to an optical scanning apparatus, and more particularly to an optical scanning apparatus which uses a multi-layered optical element system. The present invention also relates to an optical element itself, a method and apparatus for positioning and fixing the optical element. The present invention further relates to a molding tool for making the optical element.
2. Discussion of the Background
Generally, an optical scanning system using a lens system for forming an image of multiple laser beams uses known techniques including a plastic-made image forming lens capable of being instantly multi-layered corresponding to the multiple laser beams and a method of making a multi-layer lens system. Also, an optical scanning apparatus using such method of making a multi-layer lens system is known.
In particular, there is an optical scanning apparatus employed in an multi-color image forming apparatus. In such multi-color image forming apparatus, a plurality of light sources generate laser beams which are in turn directed to respective photosensitive members via a deflection mechanism and an image focusing mechanism and form separate color images according to colors on the respective photosensitive members.
Further, there is an image forming apparatus such as a digital copier and a laser printer using four photosensitive members in response to increasing demands for a high speed processing and a high image quality. This image forming apparatus forms a color image as follows. The four photosensitive members are previously aligned in parallel to each other along in a direction of sheet transferring. The photosensitive members are exposed simultaneously to light beams generated in accordance with these four photosensitive members to form latent images. The latent images are developed with different color toners: yellow, magenta, cyan, and black toners. The developed toner image in different colors are in turn overlaid in synchronism with each other into a single full-color image.
The above-described various image forming apparatuses adopt a plurality of optical scanning mechanisms; however, the adaptation results in upsizing of the apparatus. To attempt to solve this issue, an optical scanning method and apparatus has been introduced. Such optical scanning method and apparatus uses a lens system including a plurality of image focusing lenses made in a multi-layered unified form; however, in this method and apparatus, positioning of such a lens system is not appropriately established.